1. Field
The present invention relates to a light emitting diode luminaire, which includes a high power light emitting diode (LED) drive circuit, and more particularly, to an LED luminaire, which includes a plurality of light emitting groups each including a plurality of LEDs and a power factor correction unit capable of supplying stabilized drive voltage to an LED drive IC controlling the plurality of light emitting groups to be sequentially driven according to a voltage level of the drive voltage.
2. Discussion
A light emitting diode (LED) is a semiconductor device formed of gallium (Ga), phosphorus (P), arsenic (As), indium (In), nitrogen (N), aluminum (Al), and the like, and exhibiting diode characteristics, and emits blue, red, or green light upon application of electric current thereto. LEDs have been widely used in the art due to various merits such as a longer lifespan, a faster response (a period of time from a time point of receiving electric current to a time point of emitting light), and lower power consumption than electric bulbs.
Generally, a light emitting diode can be driven by direct current due to diode characteristics thereof. Accordingly, a typical LED luminaire has limited application and requires a separate circuit such as a switched-mode power supply (SMPS) in order to be driven by a domestic AC power source. As a result, the typical LED luminaire has a complicated drive circuit, causing increase in manufacturing costs.
To solve such problems, studies have been focused on development of a light emitting device capable of being driven by AC power by connecting a plurality of light emitting cells to each other in series or in parallel.
FIG. 1 is a block diagram of an AC LED luminaire in the related art, and FIG. 2 is a waveform diagram of rectified voltage and LED drive current of the AC LED luminaire shown in FIG. 1.
As shown in FIG. 1, an AC LED luminaire in the related art includes a rectifier 10 which outputs rectified voltage Vrec through full-wave rectification of AC voltage supplied from an AC voltage source (VAC), first to fourth light emitting groups 20, 22, 24, 26, which are sequentially driven by the rectified voltage Vrec, a drive controller 40 which controls sequential driving of the first to fourth light emitting groups 20, 22, 24, 26 according to a voltage level of the rectified voltage Vrec, and first to fourth light emitting group drive units SW1, SW2, SW3, SW4 each having a switching function and a constant current control function.
Referring to FIG. 2, in operation of the AC LED luminaire, the drive controller 40 determines the voltage level of the rectified voltage Vrec applied from the rectifier 10, and sequentially drives the first to fourth light emitting groups 20, 22, 24, 26 according to a voltage level of the rectified voltage Vrec.
Accordingly, in time zones in which the voltage level of the rectified voltage Vrec is greater than or equal to a first threshold voltage VTH1 and less than a second threshold voltage VTH2 (in t1˜t2 and t7˜t8 in a cycle of the rectified voltage), the drive controller 40 controls only the first light emitting group 20 to be driven by maintaining a first switch SW1 in a turn on state while maintaining a second switch SW2, a third switch SW3 and a fourth switch SW4 in a turn off state.
In addition, in time zones in which the voltage level of the rectified voltage Vrec is greater than or equal to the second threshold voltage VTH2 and less than a third threshold voltage VTH3 (t2˜t3 and t6˜t7 in a cycle of the rectified voltage), the drive controller 40 controls only the first light emitting group 20 and the second light emitting group 22 to be driven by maintaining the second switch SW2 in a turn on state while maintaining the first switch SW1, the third switch SW3 and the fourth switch SW4 in a turn off state.
Further, in time zones in which the voltage level of the rectified voltage Vrec is greater than or equal to the third threshold voltage VTH3 and less than a fourth threshold voltageVTH4 (t3˜t4 and t5˜t6 in a cycle of the rectified voltage), the drive controller 40 controls the first light emitting group 20, the second light emitting group 22 and the third light emitting group 24 to be operated by maintaining the third switch SW3 in a turn on state while maintaining the first switch SW1, the second switch SW2 and the fourth switch SW4 in a turn off state.
Further, in time zones in which the voltage level of the rectified voltage Vrec is greater than or equal to the fourth threshold voltage VTH4 (t4˜t5 in a cycle of the rectified voltage), the drive controller 40 controls the AC LED luminaire to allow all of the first to fourth light emitting groups 20, 22, 24, 26 to be driven by maintaining the fourth switch SW4 in a turn on state while maintaining the first to third switches SW1, SW2, SW3 in a turn off state.
On the other hand, in the AC LED luminaire as shown in FIG. 1, the LED drive IC has a low voltage switching withstand voltage of 500V or less and thus is vulnerable to surge voltage. In order to prevent circuit damage by surge voltage and/or inrush current, a surge protection circuit (SPC) comprised of circuit protection devices may be added to a front side of the LED drive IC, but does not provide enough surge protection effects due to too low a withstand voltage of the LED drive IC. Further, in order to solve such problems, an automatic voltage regulator (AVR), a surge protection device (SPD), and the like are separately used in the art. However, the use of the surge protection device and the like results in increase in size and manufacturing costs of the LED luminaire, so that the fundamental purpose of using the LED drive IC cannot be satisfied.
Further, in the AC LED luminaire as shown in FIG. 1, the drive controller 40, the first light emitting group drive unit SW1, the second light emitting group drive unit SW2, the third light emitting group drive unit SW3, the fourth light emitting group drive unit SW4, and the like are incorporated into a single LED drive integrated circuit (IC), which is generally used to implement the AC LED luminaire. In the LED luminaire using such an LED drive IC, output current of the LED drive IC is maintained at a constant current even upon variation of input voltage thereof, whereas output voltage of the LED drive IC varies upon variation of input voltage thereof, so that overall power consumption of the LED luminaire can be rapidly increased or decreased by variation of the input voltage. As a result, since the LED luminaire using the LED drive IC does not employ energy storage devices such as an inductor, a capacitor, and the like, LEDs act as resistors, and receives output power varying according to variation of the input voltage, causing heat generation from the LEDs and reduction in lifespan of the LEDs.
Therefore, in configuration of a high power LED luminaire using an LED drive IC, there is a need for a means for protecting the LED drive IC from surge voltage and voltage variation while ensuring fundamental purposes of the LED luminaire.